Alloy cast irons



Jan. 18, 1955 K. sPrrz 9 ALLOY CAST IRONS 2 Sheets-Sheet 1 Filed April4, 1951 Fm, L

INVENTOR. KARL SPrrz ATTORNEYS.

Jana a K, ALLOY CAST IRONS Filed April 4, 1951 2 Sheets-Sheet 2 ALLOYNo.2.

ALLOY No. 5

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7 Claims. (Cl. 75-124) This invention relates, as indicated, to alloycast irons, but has reference more particularly to ferritic andaustenitic alloy cast irons having improved mechanical and chemicalproperties.

As is well known, the atmospheric corrosion product of iron or steel,commonly known as rust, causes heavy losses, from the viewpoint ofgeneral economy.

Even irons containing fairly high percentages of nickel or copper, underattack from the oxygen and moisture contained in the atmosphere, haveformed thereon a coating of hydrated iron oxide, in the form of porousand loose flakes of rust which are easily washed away by fluid streams,or rain, or are torn away by wind. As soon as the rust is removed, theunderlying base metal is again subject to renewed attack. Moreover, rustmay even enhance further corrosion of the ferrous base metal by theformation of electrolytic oxygen concentration cells.

This form of continuous rust formation is in contrast to the protectiveoxide coatings formed on the surface of metals, such for example ascopper, aluminum and stainless steels, which coatings are insoluble,adhere firmly to the base metal, and protect the underlying base metalfrom i any continuing attack by atmospheric corroding agents.

I am aware that alloy cast irons having constituents similar to thosepresent in the alloy cast irons of my in vention, have been employed inorder to obtain improved wear resistance, as compared with unalloyedcast iron, but these are usually of low alloy content, and being, ingeneral, of a ferritic character, do not withstand atmospheric attack,and are even less able to withstand chemical, and especially acidcorrosion.

The present invention has, as its primary object the provision of alloycast irons in which are combined high tensile strengths and impactvalues with improved corrosion resistance, particularly against certainatmospheric conditions and certain dilute acids. In general, the alloycast irons of my invention are designed to prevent or at least minimizethe types of atmospheric corrosion which have been described, as well ascorrosion resulting from combustion gases, and chemical reagents,including acids.

Another object of my invention is to provide a series of alloy castirons which are capable of being readily melted, poured and cast bymeans of conventional apparatus and equipment.

A further object of the invention is to provide alloy cast irons of thecharacter described, which are adaptable for various uses, especially inthe chemical and oil industries, and for products used in many otherfields where improved wear and corrosion-resistance are a primaryfactor, as for example, cylinder linings for pumps, compressors,combustion engines, etc.

A further object of the invention is to provide alloy cast irons whichare especially useful for products in the plumbing and drainageindustries, wherein the products are subjected not onlyv to naturalatmospheric corrosion,

but also to smoke, combustion gases, moist sulphur di-' oxide, saltspray. and industrial waste liquors containing acids, chemicals, andother corrodents. Among these products are roof drain domes, floor, rampand trench drains and gratings, backwater valves, grease and oilinterceptors, roof, floor, shower and area drains. Improved impactresistance is an especially important desideratum for floor, ramp andtrench drains and gratings, because ihedsame dimensional constructionwill allow for heavier oa s.

2,699,992 Patented Jan. 18, 1955 A further object of the invention is toprovide alloy cast irons which may be used as substitutes for nonferrousalloys, such as brass, bronze, nickel-silver, etc., whereby a saving incritical or strategic materials is effected.

A still further object of the invention is to reduce the weight ofcastings for the above purposes, by reason of the increased strength ofthe alloys.

Other objects and advantages of my invention will become apparent duringthe course of the following description.

For a graphic understanding of the. characteristics and properties ofthe alloy cast irons of my invention, reference may be had to theaccompanying drawings, forming a part ofthis application, and in whichFigs. 1, 2 and 3 are photomicrographs of specific alloys coming withinthe scope of my invention, and

Fig. 4. is a drawing illustrating graphically the results of moistsulphur dioxide tests on the above specific alloys, and on aconventional cast iron.

The alloy cast irons of my invention contain at least 50% iron, morethan 1.7% to about 4% carbon, and four major alloying constituents orelements, namely, Qhromium, nickel, copper and molybdenum, each beingpresent in an amount in excess of 0.40%, with at least one being presentin an amount in excess of 1.00%. I have further found that the desiredcharacteristics toward which my invention is directed are generallyobtainable without having the chromium, nickel, copper and molybdenumpresent in an amount in excess of about 36% each, with the singlereservation that in those cases where the amount of any one of theprincipal alloying constitutents, chromium, nickel, copper andmolybdenum, is in excess of 18% each of the other three must be presentin an amount in excess of 1%, in order to provide efiectively balancedalloys in accordance with the invention. The alloy cast irons alsocontain silicon. in amounts of from 1.25% to 5.6%, manganese in amountsof from .20% to 3.0%, sulphur in amounts of from .03% to 1.00%,phosphorus in amounts of .02% to 2.00%, and aluminum in amounts of .05%to 1.00%. These constituents, namely silicon, manganese, sulphur,phosphorus and aluminum, when present, are intended to be comprised orincluded within the expression the balance of the alloy beingsubstantially iron, as hereinafter employed in the claims, since theyare normally found in cast irons.

The alloy cast irons may be prepared by any of the usual methodsemployed for making alloys. Among these methods are:

1. Melting a conventional cast iron charge in an electric furnace, andadding the alloying constituents thereto in order to obtain the desiredcomposition.

2. Melting a conventional cast iron charge in a cupola, transferringthis unalloyed cast .iron to an electric or air furnace, and then addingthe alloying'constituents to the cast iron, as usual in duplexing.

3. Melting a master alloy containing the alloying constituents in anelectric furnace, and then adding this master alloy to the conventionalcupola-melted cast iron, in a ladle, mixer, or at the spout of thecupola, to form the alloy of the desired composition.

The alloy cast irons of the present invention are generallycharacterized by high tensile strengths and impact values. They arewear-resistant and resistant both to atmospheric corrosion and tocorrosion by dilute acids and other chemicals. They can be melted,poured and cast by means of conventional apparatus and equipmentgenerally employed in steel mills and foundries for these purposes. Theyare well adapted for use in the chemical and oil industries and forproducts used in many other fields, where improved wear antfcorrosion-resistance are primary considerations, as for example,cylinder linings forpumps, compressors, combustion engines, etc. Theyare especially useful for products in the plumbing and drainageindustries, which are subjected not only to natural atmosphericcorrosion, but also to smoke, combustion gases, moist sulphur dioxide,salt spray and industrial waste liquors containing acids and othercorrodents.

(b) sulphuric acid:

Loss in grams in 1 hr 5.0353 1985 0178 5. 6605 (c) Moist sulphur dioxide(6% H2803) #1 #2 #2 Cast iron Gain in grams in 18 hrs 3234 7723 54056626 Gain in grams in 24 hrs 0079 7839 5513 1724 Gain or Loss in gramsin 42 hrs 1293 7449 5477 4727 Gain or Loss in ams in 66 hrs l i 24725639 5074 2472 Gain or Loss in grams in 72 n hrs 3642 5549 4993 7550 Theresults of these moist sulphur dioxide tests are illustrated graphicallyin Fig. 4 of the drawings.

These show that conventional cast iron deteriorates rapidly within atest period of 72 hours, and that alloy No. 1 deteriorates to a lesserdegree, but shows a markedly improved resistance, as compared with suchconventlonal cast iron. The reason for this is that the film formed bythe corroded metals (indicated by the gains in weight) is washed awayand does not protect the underlying metal which, therefore, is steadilyattacked, as indicated by loss of weight after 24 hours. Alloys Nos. 2and 3 are attacked considerably during a period of 24 hours, as 1ndrcated by the gain in weight. In contrast, however, with the conventionalcast iron, the film which is formed in alloys Nos. 2 and 3 apparently isnot easily dissolved and protects the underlying metal, as indicated bythe slow loss in weight between 24 hours and 72 hours. At that point,there already exists a difference in resistance between the cast iron(.7556) and alloy No. 3 (-|-.4993), whlch is of fundamental magnitude infavor of alloy No. 3. More specifically, the total change between 24hours and 72 hours for the cast iron is and for the same period foralloy No. 3

In other words, the total corrosion of the cast iron during the 24-72hour period is more than 1700% higher than that of alloy No. 3.

Humidity tests conducted in a humidity chamber for 72 hours at 100%humidity, and 100 F. showed markedly superior resistance of alloys Nos.1, 2 and 3, as compared with conventional cast iron.

Salt spray tests in a 20% solution, at 95 F. resulted in improvedperformance of the alloys in the following order: Alloy No. 3, alloy No.2, and No. 1, with the conventional cast iron least resistant.

Alloys Nos. 1, 2 and 3 were selected for the above tests, primarilybecause of the fact that they utilize in their composition relativelysmall amounts of the critical or strategic alloying metals.

It is apparent from the foregoing that I have provided two series orgroups of alloy cast irons, all of which are corrosion-resistant, withone group having tensile strengths of from about 38,000 to about 50,000p. s. i., and being well adapted for use in the plumbing and drainagefields, and the other group having tensile strengths in excess of 50,000p. s. i., and being generally suitable for application or uses in thechemical industries, being heat and wear resistant, as well ascorrosion-resistant; that one group utilizes minimum amounts ofstrategic metals, and that both groups are capable of being readilymelted, poured and cast, by means of conventional apparatus andequipment.

It is to be understood that the particular alloy cast irons hereinlisted are exemplary and illustrative of desirable alloy compositions,and that slight changes may be made in the proportions of the alloyswithout departing from the spirit of the invention as defined in thesubjoined claims.

Having thus described my invention, I claim:

1. A corrosion-resistant alloy cast iron containing about 3.32% carbon,about 0.60% chromium, about 1.03% nickel, about 0.45% copper, about0.48% molybdenum, from 1.25% to 5.6% silicon, from 0.20% to 3.0%manganese, from 0.03% to 1.00% sulphur, from 0.02% to 2.00% phosphorus,from 0.05% to 1.00% aluminum, and the remainder being iron.

2. A corrosion-resistant alloy cast iron containing about 2.90% carbon,about 2.04% chromium, about 3.69% nickel, about 1.18% copper, about0.88% molybdenum, from 1.25 to 5.6% silicon, from 0.20% to 3.0%manganese, from 0.03% to 1.00% sulphur, from 0.02% to 2.00% phosphorus,from 0.05% to 1.00% aluminum, and the remainder being iron.

3. A corrosion-resistant alloy cast iron containing about 3.25% carbon,about 12.40% chromium, about 17.60% nickel, about 5.70% copper, about7.20% molybdenum, from 1.25% to 5.6% silicon, from 0.20% to 3.0%manganese, from 0.03% to 1.00% sulphur, from 0.02% to 2.00% phosphorus,from 0.05 to 1.00% aluminum, and the remainder being iron, but the ironbeing always in excess of 50%.

4. A corrosion-resistant alloy cast iron containing about 3.40% carbon,about 4.60% chromium, about 16.30% nickel, about 15.80% copper, about5.20% molybdenum, from 1.25% to 5.6% silicon, from 0.20% to 3.0%manganese, from 0.03% to 1.00% sulphur, from 0.02% to 2.00% phosphorus,from 0.05 to 1.00% aluminum, and the remainder being iron, but the ironbeing always in excess of 50%.

5. A corrosion-resistant alloy cast iron containing more than 1.7% toabout 4% carbon, chromium, nickel, copper and molybdenum, each in excessof 0.40%, but not in excess of 36%, with at least one in excess of 1%,silicon in amounts of from 1.25% to 5.6%, manganese in amounts of from0.20% to 3.0%, sulphur in amounts of from 0.03% to 1.00%, phosphorus inamounts of from 0.02% to 2.00%, aluminum in amounts of from 0.05 to1.00%, the remainder being iron, but the iron being always in excess of50%.

6. A corrosion-resistant alloy cast iron, as defined in claim 5, inwhich if any one of the principal alloying ingredients, chromium,nickel, copper and molybdenum, is present in excess of 18%, all of theothers are present in excess of 1%.

.7. A corrosion-resistant alloy cast iron containing more than 1.7% toabout 4% carbon, chromium, nickel, copper and molybdenum, each in anamount in excess of 0.40%, but not in excess of about 36%, with at leastone in an amount in excess of 1.00%, but each of the others in excess of1.00%, when any one is in excess of 18%, silicon in amounts of from1.25% to 5.6%, manganese in amounts of from 0.20% .to 3.0%, sulphur inamounts of from 0.03% to 1.00%, phosphorus in amounts of from 0.02% to2.00%, aluminum in amounts of from 0.05% to 1.00%, the remainder beingiron, but the iron being always in excess of 50%.

References Cited in the file of this patent UNITED STATES PATENTS1,528,478 Hadfield Mar. 3, 1925 1,876,411 Gregg et a1. Sept. 2, 19322,214,652 Bancroft Sept. 10, 1940 FOREIGN PATENTS 150,367 SwitzerlandJan. 2, 1932 593,298 Great Britain Oct. 14, 1947

1. A CORROSION-RESISTANT ALLOY CAST IRON CONTAINING ABOUT 3.23% CARBON,ABOUT 0.60% CHROMIUM, ABOUT 1.03% NICKEL, ABOUT 0.45% COPPER, ABOUT0.48% MOLYBDENUM, FROM 1.25% TO 5.6% SILICON, FROM 0.20% TO 3.0%